强度弱化导向的超高温热处理后Q345B钢材性能研究及其在防屈曲支撑中的应用

为研究超高温热处理技术对我国常用Q345B热轧钢材强度的影响规律，以及在减震设计中的应用，完成7个不同参数的超高温热处理及缓慢冷却后的钢材单向拉伸材性试验，研究了热处理极限温度以及冷却速率对于钢材强度及延性的影响。通过3个热处理前后钢材的循环荷载材性试验，得到钢材在循环荷载作用下强度和塑性发展规律，并拟合得到可应用于有限元分析的Chaboche循环本构模型。通过有限元分析了两种局部低强防屈曲支撑，以探讨该种超高温热处理技术在减震设计中的适用性。结果表明：Q345钢材在热处理后强度降低，其强度削弱程度随着热处理极限温度的升高和降温速率的减缓而增加；热处理后的钢材在循环荷载作用下屈服点及屈服平台消失，循环强化现象明显；所设计的2种局部低强防屈曲支撑在循环荷载作用下塑性发展主要发生在热处理段，且具有良好的耗能能力。

Effect of strength weakening oriented heat treatment on Q345Bsteel and its application on buckling restrained brace

To investigate the effect of heat treatment on Chinese Q345B steel and the application potential on aseismic design, seven tensile tests with different peak temperatures and cooling rates were conducted on Q345B material specimens to investigate the effect on material strengths and ductility. Three cyclic loading tests were conducted to study the plasticity development under cyclic loading, and a Chaboche model was fitted out that can be applied to the finite element simulations. Then two local strength weakened buckling restrained braces were designed and simulated by FEA to explore the application of this strength weakening oriented heat treatment on energy dissipation device design. The results show that Q345B steel has an effective strength weakening behaviors after experiencing this heat treatment. And the weakening effect is more obvious with the increase of peak temperature and the decrease of cooling rate. The heat treated steel does not exhibit its yield plateau under cyclic loading and presents a more obvious cyclic hardening behavior. The two simulated local strength weakened buckling restrained braces show satisfactory plasticity development and energy dissipation ability at heat treated region.